The present invention relates to alarm systems, and more particularly to alarm systems for display cases such as those for cigarette cartons.
A wide variety of display cases has been developed for displaying products and making the products accessible for customer removal. Such display cases are used in particular for the vending of cigarette cartons. Typically, such cases include a plurality of shelves on which the cartons are stacked and a security shield or gate on each shelf to permit only the bottom carton on each shelf to be withdrawn. The cartons remaining on the shelf then drop to fill the void created by removal of the bottom carton.
Unfortunately, theft or pilferage from such display cases is an increasingly common problem. Often, the cases are located in convenience stores or gas stations wherein the employees cannot give their full attention to the monitoring of all products within the store. Because of the large number of cartons available within the display case, a shoplifter may easily remove a number of cartons within a few seconds.
Prior artisans have attempted to develop alarm systems for such cases. One weight-actuated system is illustrated in U.S. Pat. No. 4,819,015 issued Apr. 4, 1989 to Bullivant et al and entitled ANTI-THEFT PRODUCT RACK AND METHOD. The Bullivant case includes a number of weight-sensing detectors for monitoring the weight of product within the case. A control system is coupled to the weight sensors, and weight deviations are monitored and distinguished as either a disturbance or a product removal. Based on this distinction, the control circuit then determines whether a theft or pilferage pattern has occurred. The control system sounds an alarm if such a pattern is detected. However the Bullivant alarm system is not without its drawbacks. First, the weight sensors are subject to miscalibration--both initially and during subsequent use. Second, the control circuitry must be sophisticated to discriminate between disturbances and removals and then to further distinguish between theft conditions and acceptable product movement. Third, all of the product within the display case is accessible simultaneously to the consumer. This results in cartons being accidentally knocked out of the case and also creates a more attractive target for the shoplifter.
Optical detection systems are known in the hotel room bar vending area. Exemplary teachings are provided in U.S. Pat. No. 4,791,411 issued Dec. 13, 1988 to Staar and entitled MANUAL FREE-ACCESS VENDING MACHINE; and U.S. Pat. No. 4,629,090 issued Dec. 16, 1986 to Harris et al and entitled HOTEL ROOM BAR WITH OPTICAL SENSING SYSTEM. The Staar system includes an optical detector associated with each product location. The Harris system includes an optical sensor at each product exit opening. In both systems, the optical detectors sense product removal, and the systems provides an automatic billing function in response to such removal. These systems are not designed to, and do not provide, any type of alarm. Further, they make no attempt to distinguish between acceptable and unacceptable product removal.